Oil injecting apparatus

ABSTRACT

The opening of an oil container  11  for storing oil  12  is sealed airtight with a cover member  32 . A one-sided-bag-shaped fluid dynamic pressure bearing  10  is seated on an O-ring  25  and fixed airtight onto the upper surface of a bearing seating  30 . Inanexhaust position with the distal end portion of an injection tube  36  positioned away from an oil level, the inside of the oil container 11 is evacuated by a vacuum pump  22  through a suction/exhaust passage including a suction/exhaust through-hole  17 , thus turning the inside of the one-sided-bag-shaped fluid dynamic pressure bearing ( 10 ) into a vacuum. In this state, a control device drives a moving device to raise the oil container  11  to an injection position and releases the suction/exhaust passage to the atmosphere. This causes the oil  12  to be injected into the one-sided-bag-shaped fluid dynamic pressure bearing  10  through an oil injection passage including the injection tube  36 .

TECHNICAl FIELD

The present invention relates to an apparatus for injecting oil into aone-sided-bag-shaped fluid dynamic pressure bearing by a vacuuminjection method.

The term “one-sided-bag-shaped fluid dynamic pressure bearing” as usedherein refers to a fluid dynamic pressure bearing composed of bearingcomponents including a shaft and a sleeve, and oil injected into aminute gap formed between those bearing components, the fluid dynamicpressure bearing having only one oil injection port for oil injectioninto the minute gap.

BACKGROUND ART

As is well known, rolling bearings have been widely adopted for motorsthat drive 3.5-inch discs. However, fluid dynamic pressure bearings areincreasingly being adopted for small motors that drive smaller discssuch as 2.5-inch or 1.0-inch discs instead of rolling bearings.

As shown, for example, in FIG. 6, such a fluid dynamic pressure bearingincludes a flanged shaft 1 serving as a rotary bearing member, a steppedclosed-end sleeve 4 serving as a stationary bearing member, a thrustretainer plate 5 serving as an annular cover member, and lubricating oilinjected into a minute gap formed by those members.

The flanged shaft 1 includes a cylinder portion 2 and an annular flangeportion 3 that are integrated with each other. A lower part of thecylinder portion 2 of the flanged shaft 1 serves as a radial dynamicpressure bearing cylinder portion, with radial dynamic pressuregenerating grooves G1 formed on the outer peripheral surface thereof.Further, an upper part of the cylinder portion 2 of the flanged shaft 1serves as a rotor-mounting cylinder portion, with a rotor-hub-mountingcylinder portion of a small diameter being formed at its distal end.

The annular flange portion 3 of the flanged shaft 1, which functions asa disc-shaped thrust plate, has thrust dynamic pressure generatinggrooves formed respectively on its upper and lower surfaces.

The stepped closed-end sleeve 4 has a lower cylinder portion of a smalldiameter and an upper cylinder portion of a larger diameter. An openingwith a still larger diameter is formed at the upper end portion of theupper cylinder portion. The thrust retainer plate 5 is fitted airtightinto this opening, whereby the opening of the stepped closed-end sleeve4 is sealed airtight with the thrust retainer plate 5. Formed at theboundary between the small-diameter lower cylinder portion and thelarge-diameter upper cylinder portion is an annular step portion servingas the bottom portion of the upper cylinder portion.

Between the flanged shaft 1, the stepped closed-end sleeve 4, and thethrust retainer plate 5, there are formed a cylindrical minute gap R1,an annular minute gap R2, a cylindrical minute gap R3, an annular minutegap R4, a cylindrical minute gap R5, and a disc-shaped minute gap R6.Although somewhat exaggerated in FIG. 6, the sizes of the minute gaps R1through R6 range from ten to several tens μ in the case of small andthin fluid dynamic pressure bearings used in small and thin motors.

It is to be noted that the minute gaps R3 and R6, each functioning as anoil reservoir, are formed wider than the other minute gaps. Lubricatingoil is injected into these minute gaps by a vacuum injection method fromthe annular opening of the cylindrical minute gap R1.

The inner peripheral surface of the thrust retainer plate 5 forms anoutwardly tapered surface. Accordingly, when seen in cross section, thecylindrical minute gap R1 formed between the inner peripheral surface ofthe thrust retainer plate 5 and the upper outer peripheral surface ofthe cylinder portion 2 forms a tapered gap that is tapered outwardlyfrom the inner to outer portions of the bearing. The resulting capillaryaction and surface tension form a capillary seal portion S thatfunctions to prevent the lubricating oil from leaking outside of thebearing. Further, the cylindrical minute gap R3 serves as an oilreservoir for thrust dynamic pressure bearing, and the disc-shapedminute gap R6 serves as an oil reservoir for radial dynamic pressurebearing.

As described above, the one-sided-bag-shaped fluid dynamic pressurebearing shown in FIG. 6 includes the flanged shaft 1, the. steppedclosed-end sleeve 4, the thrust retainer plate 5 that is an annularcover member, and oil for lubrication injected into a minute gapconsisting of the plurality of minute gaps R1 to R6 that arecommunicated with each other and formed between those components. Thisminute gap defines a one-sided-bag-shaped minute gap, with the openingof the minute gap R1, which opens to the atmosphere, serving as the onlyopening of this minute gap.

Although it is not easy to inject oil into such a one-sided-bag-shapedfluid dynamic pressure bearing having a one-sided-bag-shaped minute gap,some injection methods have already been developed to this end, such asthe vacuum injection methods disclosed in U.S. Pat. No. 5601125 (PatentDocument 1), U.S. Pat. No. 5862841 (Patent Document 2), and U.S. Pat.No. 5894868 (Patent Document 3).

As shown in FIG. 5, for example, a conventional oil injecting apparatusemploying a vacuum injection method includes an oil container 11 storingan oil 12 to a predetermined level, a cover member 13 having an oilinjection through-passage 15 and a suction/exhaust through-passage 17, abellows 11 a that is secured airtight to the back surface of the covermember 13 at one end and to the opening of the oil container 11 at theother end, an injection tube 14 whose distal end projects straight intothe oil container 11 and whose other end is connected to the oilinjection through-passage 15, a suction/exhaust tube 16 whose distal endprojects straight into the oil container 11 and whose other end isconnected to one end of the suction/exhaust through-passage 17 of thecover member 13, a suction/exhaust device connected to the other end ofthe suction/exhaust through-passage 17 of the cover member 13, a movingdevice that vertically moves the oil container 11 from an exhaustposition (FIG. 5 (A)) with the distal end of the injection tube 14positioned away from the oil level into an injection position (FIG.5(B)) with the distal end of the injection tube 14 submerged into theoil, and bearing fixing means for fixing the one-sided-bag-shaped fluiddynamic pressure bearing 10, into which the oil 12 is to be injected,onto the cover member 13 with its surface on the oil injection port sidebeing seated on an O-ring 25.

The suction/exhaust device includes a vacuum pump 22, suction/exhausttubes 18, 20, 21, and valves 23, 24. The moving device includes astepping motor 27 and an oil container holder 28. Further, the bearingfixing means forms a part of a holding device (not shown) holding thecover member 13.

Oil injection is performed as follows with such a conventional oilinjecting apparatus. First, in the exhaust position (FIG. 5(A)) with thedistal end of the injection tube 14 positioned away from the oil levelinside the oil container 11, a control device (not shown) opens thevalve 23 and closes the valve 24, and activates the vacuum pump 22. Asthis happens, the inside of the oil container 11 is evacuated throughthe suction/exhaust tube 16, the suction/exhaust through-hole 17, andthe suction/exhaust tubes 18 and 20; at the same time, the inside of theone-sided-bag-shaped fluid dynamic pressure bearing 10, whichcommunicates with the inside of the oil container 11 through theinjection tube 14 and the oil injection through-hole 15, is alsoevacuated into a vacuum.

Then, in this state, the control device drives the moving device toraise the oil container 11, whereby the distal end of the injection tube14 is submerged into the oil 12. Subsequently, in this injectionposition (FIG. 5(B)), the control device closes the valve 23 and opensthe valve 24. As this happens, the inside of the oil container 11 iscommunicated with the atmosphere through the suction/exhaust tube 16,the suction/exhaust through-hole 17, and the suction/exhaust tubes 18and 21, and thus turned into the atmospheric pressure. This causes theoil 12 in the oil container 11 to be injected into theone-sided-bag-shaped fluid dynamic pressure bearing 10.

Incidentally, the conventional oil injection apparatus described aboveis equipped with an extendable part such as a bellows for verticallymoving-the oil container. This bellows is formed of a rubber materialand hence liable to deform when placed in a high vacuum. Suchdeformation of the bellows makes it difficult to maintain a high vacuumdegree with good accuracy, resulting in poor durability. This leads to aproblem in that the bellows must be exchanged frequently in order tomaintain this accuracy. In short, the conventional oil injectingapparatus described above is poor in operability, resulting in anincrease in maintenance cost.

An object of the present invention is to provide an oil injectingapparatus for injecting oil into a one-sided-bag-shaped fluid dynamicpressure bearing by a vacuum injection method, the apparatus providinggood operability and low maintenance cost.

DISCLOSURE OF THE INVENTION

To attain the above object, in an oil injecting apparatus for injectingoil into a one-sided-bag-shaped fluid dynamic pressure bearing by avacuum injection method, an injection tube is disposed so as to bemovable while passing through a cover of an oil container, withairtightness being retained by an O-ring, and the distance between theoil container and a bearing seating, onto which the one-sided-bag-shapedfluid dynamic pressure bearing to be injected with oil is mounted andfixed airtight, is changed to thereby effect a change from an exhaustposition to an injection position.

That is, an oil injecting apparatus for a one-sided-bag-shaped fluiddynamic pressure bearing which is designed to attain the above-mentionedobject includes: a bearing seating having a bearing seating surfaceformed on a front surface thereof and an oil injection through-passageextending through the bearing stand from the front surface to a backsurface thereof; an oil container storing oil to a predetermined leveland sealed with a cover member provided with an injection tubepass-through hole; a suction/exhaust tube having one end projecting intothe oil container and the other end connected to a suction/exhaustdevice; an injection tube passing through the injection tubepass-through hole of the cover member such that the injection tube iscapable of vertical movement while maintaining airtightness, theinjection tube having a lower end projecting into the oil container andan upper end secured to a lower end of the oil injection through-passageof the bearing seating; a distance changing device which changes adistance between the bearing seating and the oil container from anexhaust position with the lower end of the injection tube positionedaway from an oil level into an injection position with the lower end ofthe injection tube submerged into oil; and bearing fixing means abuttinga one-sided-bag-shaped fluid dynamic pressure bearing into which oil isto be injected, for fixing airtight the one-sided-bag-shaped fluiddynamic pressure bearing onto the bearing seating.

Further, the one-sided-bag-shaped fluid dynamic pressure bearing isfixed onto the cover member by the bearing fixing means, an inside ofthe one-sided-bag-shaped fluid dynamic pressure bearing is brought intoa vacuum in the exhaust position by the suction/exhaust device, and thenin the injection position, the suction/exhaust tube is released to theatmosphere to inject oil in the oil container into theone-sided-bag-shaped fluid dynamic pressure bearing.

The change from the exhaust position to the injection position iseffected through vertical movement of the bearing seating or the oilcontainer.

The distance changing device is, for example, a stepping motor, ahydraulic motor, an air cylinder, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view schematically showing an oil injectingapparatus for a one-sided-bag-shaped fluid dynamic pressure bearingaccording to a first embodiment of the present invention in an exhaustposition.

FIG. 2 is a sectional view schematically showing the oil injectingapparatus for the one-sided-bag-shaped fluid dynamic pressure bearingaccording to the first embodiment of the present invention in aninjection position.

FIG. 3 is a sectional view schematically showing an oil injectingapparatus for a one-sided-bag-shaped fluid dynamic pressure bearingaccording to a second embodiment of the present invention in an exhaustposition.

FIGS. 4 are a front view (A) and a side view (B) of the oil injectingapparatus for a one-sided-bag-shaped fluid dynamic pressure bearingaccording to the first embodiment of the present invention.

FIGS. 5 is a sectional view schematically showing a conventional oilinjecting apparatus for a one-sided-bag-shaped fluid dynamic pressurebearing.

FIG. 6 is a sectional view of a one-sided-bag-shaped fluid dynamicpressure bearing, showing minute gaps in somewhat exaggerated sizes.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIGS. 1, 2, and 4, an oil injecting apparatus according to afirst embodiment of the present invention includes a bearing seating 30having a bearing seating surface formed on its front surface and an oilinjection through-passage 31 extending through the bearing seating 30from this front surface to the back surface thereof, a cover member 32provided with an injection tube pass-through hole 33 and asuction/exhaust through-hole 34, an oil container 11 storing an oil 12to a predetermined level and sealed with the cover member 32, asuction/exhaust tube 18 whose one end is connected to one end of thesuction/exhaust through-hole 34 of the cover member 32 and whose otherend is connected to a suction/exhaust device, an injection tube 36, adistance changing device for changing the distance between the bearingseating 30 and the oil container 11, and bearing fixing means 26 forfixing airtight onto the bearing seating 30 a one-sided-bag-shaped fluiddynamic pressure bearing 10, into which oil is to be injected, with itssurface on the oil injection port side being seated and abutted onto anO-ring 25.

The injection tube 36 with a flat outer peripheral surface passesthrough the injection tube pass-through hole 33, which has a flat innerperipheral surface, in an airtight manner and so as to be verticallymovable, with the lower end of the injection tube 36 projecting into theoil container 11 and the upper end thereof being secured to the lowerend of the oil injection through-passage 31 of the bearing seating 30.The airtightness between the injection tube pass-through hole 33 and theinjection tube 36 is secured by an O-ring 35 arranged in the injectiontube pass-through hole 33. The airtightness can be further enhanced byproviding the O-ring 35 in two, three, and more stages.

The distance changing device serves to change the distance between theoil container 11 and the bearing seating 30 so as to bring the oilinjecting apparatus from an exhaust position (FIG. 1) with the lower endof the injection tube 36 positioned away from the oil level into aninjection position (FIG. 2) with the lower end of the injection tube 36submerged into the oil. As shown in FIG. 4, the distance changing deviceincludes a hydraulic pump 27 and an oil container holder 28, andraises/lowers the oil container 11 with respect to the bearing seating30 whose position is fixed, thereby changing the distance between theoil container 11 and the bearing seating 30.

The suction/exhaust device includes a vacuum pump 22, suction/exhausttubes 20, 21, and valves 23, 24.

Oil injection is performed as follows with the oil injecting apparatusaccording to the first embodiment of the present invention. First, inthe exhaust position (FIG. 1) with the distal end of the injection tube14 positioned away from the oil level in the oil container 11, a controldevice (not shown) opens the valve 23 and closes the valve 24, andactivates the vacuum pump 22. As this happens, the inside of the oilcontainer 11 is evacuated, and at the same time, the inside of theone-sided-bag-shaped fluid dynamic pressure bearing 10, whichcommunicates with the inside of the oil container 11 through theinjection tube 36 and the oil injection through-passage 31, is alsoevacuated into a vacuum.

Then, the control device drives the hydraulic pump 27 to move the oilcontainer 11 into the injection position (FIG. 2), whereby the lower endof the injection tube 36 is submerged into the oil 12 in the oilcontainer 11. Subsequently, the control device closes the valve 23 andopens the valve 24. As this happens, the inside of the oil container 11is communicated with the atmosphere through the suction/exhaustthrough-hole 34, and the suction/exhaust tubes 18 and 21, and thusturned into the atmospheric pressure. This causes the oil 12 in the oilcontainer 11 to be injected into the one-sided-bag-shaped fluid dynamicpressure bearing 10.

As shown in FIG. 3, an oil injection apparatus according to a secondembodiment of the present invention includes a bearing seating 30 havinga bearing seating surface formed on its front surface and an oilinjection through-passage 31 extending through the bearing seating 30from this front surface to the back surface thereof, a cover member 32provided with an injection tube pass-through hole 33 and asuction/exhaust through-hole 34, an oil container 11 storing an oil 12to a predetermined level and sealed with the cover member 32, asuction/exhaust tube 18 whose one end is connected to one end of thesuction/exhaust through-hole 34 of the cover member 32 and whose otherend is connected to a suction/exhaust device, an injection tube 36, adistance changing device for changing the distance between the bearingseating 30 and the oil container 11, and bearing fixing means 26 forfixing airtight onto the bearing seating 30 a one-sided-bag-shaped fluiddynamic pressure bearing 10, into which oil is to be injected, with itssurface on the oil injection port side being seated and abutted onto anO-ring 25.

The injection tube 36 with a male thread 36 a formed on an intermediatesection thereof passes through the injection tube pass-through hole 33,which is provided with a female thread 33 a that threadedly engages withthe male thread 36 a, in an airtight manner and so as to be verticallymovable, with the lower end of the injection tube 36 projecting into theoil container 11 and the upper end thereof being secured to the lowerend of the oil injection through-passage 31 of the bearing seating 30.The airtightness between the injection tube pass-through hole 33 and theinjection tube 36 is secured by an O-ring 35 arranged in the injectiontube pass-through hole 33.

The distance changing device serves to change the distance between theoil container 11 and the bearing seating 30 so as to bring the oilinjecting apparatus from an exhaust position with the lower end of theinjection tube 36 positioned away from the oil level into an injectionposition with the lower end of the injection tube 36 submerged into theoil. The distance changing device includes a stepping motor (not shown),and rotates and vertically moves the bearing seating 30, onto which theone-sided-bag-shaped fluid dynamic pressure bearing 10 to be injectedwith oil is fixed airtight, thereby changing the relative distance fromthe oil container 11 whose position is fixed.

The suction/exhaust device includes a vacuum pump 22, suction/exhausttubes 20, 21, and valves 23, 24.

The oil injecting apparatus employing a vacuum injection methodaccording to the second embodiment of the present invention is the sameas the oil injecting apparatus employing a vacuum injection methodaccording to the first embodiment described above, except for thedistance changing means for changing the distance between the oilcontainer and the bearing seating, onto which the one-sided-bad-shapedfluid dynamic pressure bearing to be injected with oil is seated andfixed airtight.

That is, in the first embodiment, as the distance changing means foreffecting a change from the exhaust position to the injection position,the outer peripheral surface of the injection tube 36 and the innerperipheral surface of the injection tube pass-through hole 33 of thecover member 32 are both formed as flat surfaces, and the oil container11 is moved without being rotated, thereby changing the relativedistance of the oil container 11 from the bearing seating 30 onto whichthe one-sided-bag-shaped fluid dynamic pressure bearing 10 to beinjected with oil is fixed airtight.

In contrast, in the second embodiment, as the distance changing meansfor effecting a change from the exhaust position to the injectionposition, the male thread is formed on a part of the outer peripheralsurface of the injection tube 36 and brought into threaded engagementwith the female thread formed on a part of the inner peripheral surfaceof the injection tube pass-through hole 33 of the cover member 32, andthe bearing seating 30, onto which the one-sided-bag-shaped fluiddynamic pressure bearing 10 to be injected with oil is fixed airtight,is rotated for vertical movement, thereby changing the relative distanceof the bearing seating 30 from the oil container 11 whose position isfixed.

INDUSTRIAL APPLICABILITY

According to the present invention, in the oil injecting apparatus forinjecting oil into a one-sided-bag-shaped fluid dynamic pressure bearingby a vacuum injection method, the injection tube is disposed so as to bemovable while passing through the oil container cover, with airtightnessbeing retained by the O-ring, and the distance between the oil containerand the bearing seating, onto which the one-sided-bag-shaped fluiddynamic pressure bearing to be injected with oil is fixed airtight, ischanged to thereby effect a change from the exhaust position to theinjection position.

Therefore, as compared with conventional oil injecting apparatusesequipped with an extendable part such as a bellows, the presentinvention can provide an oil injecting apparatus for aone-sided-bag-shaped fluid dynamic pressure bearing which provides goodoperability and low maintenance cost.

1. An oil injecting apparatus comprising: a bearing seating having abearing seating surface formed on a front surface thereof and an oilinjection through-passage extending through the bearing seating from thefront surface to a back surface thereof: a cover member having aninjection tube pass-through hole and a suction/exhaust through-passage;an oil container storing oil to a predetermined level and sealed withthe cover member; a suction/exhaust tube having one end connected to thesuction/exhaust through-passage and the other end connected to asuction/exhaust device; an injection tube passing through the injectiontube pass-through hole of the cover member such that the injection tubeis capable of vertical movement while maintaining airtightness, theinjection tube having a lower end projecting into the oil container andan upper end secured to a lower end of the oil injection through-passagepassage of the bearing seating; a distance changing device which changesa distance between the bearing seating and the oil container from anexhaust position in which the lower end of the injection tube ispositioned away from an oil level to an injection position in which thelower end of the injection tube is submerged into oil; and bearingfixing means abutting a one-sided-bag-shaped fluid dynamic pressurebearing into which oil is to be injected, for fixing airtight theone-sided-bag-shaped fluid dynamic pressure bearing onto the bearingseating; wherein the one-sided-bag-shaped fluid dynamic pressure bearingis fixed onto the cover member by the bearing fixing means, an inside ofthe one-sided-bag-shaped fluid dynamic pressure bearing is brought intoa vacuum in the exhaust position by the suction/exhaust device, and thenin the injection position, the suction/exhaust tube is released to anatmosphere to inject oil in the oil container into theone-sided-bag-shaped fluid dynamic pressure bearing. 2-5. (canceled) 6.An oil injecting apparatus according to claim 1; wherein the distancechanging device vertically moves the bearing seating.
 7. An oilinjecting apparatus according to claim 1; wherein the distance changingdevice vertically moves the oil container (11).
 8. An oil injectingapparatus according to claim 7; wherein the distance changing deviceincludes a stepping motor.
 9. An oil injecting apparatus according toclaim 6; wherein the distance changing device includes a stepping motor.10. An oil injecting apparatus according to claim 5; wherein thedistance changing device includes a stepping motor.
 11. An oil injectingapparatus according to claim 7; wherein the distance changing deviceincludes a hydraulic motor.
 12. An oil injecting apparatus according toclaim 6; wherein the distance changing device includes a hydraulicmotor.
 13. An oil injecting apparatus according to claim 5; wherein thedistance changing device includes a hydraulic motor.